EFFECT OF WATER POTENTIAL ON MICROBIAL ANTAGONISM TO PYRENOPHORA-TRITICI-REPENTIS IN WHEAT RESIDUE

Selected fungi belonging to identifiable ecological associations in reduced-tillage wheat straw were tested for their ability to grow, and to inhibit growth and pseudothecia production by Pyrenophora tritici-repentis, in infested wheat residue at several water potentials. Fungi from the pioneer-colonizer association were little affected by water potential from -0.1 to -7.0 MPa, and were not antagonistic to P. tritici-repentis. Fungi from buried straw were commonly sensitive to water stress, and some were antagonistic to growth of P. tritici-repentis. Few fungi were inhibitory to pseudothecia production by the pathogen; these were mostly associated with straw from the soil contact area of the mulch layer. Bacteria were shown to reduce pseudothecia formation also. All examples of pseudothecia inhibition occurred only at the wettest level tested, -0.1 MPa.